The invention relates to a device for positioning an optical fiber with respect to a defined reference plane. The optical fiber is arranged so as to be displaceable with respect to the reference plane by means of an electromechanical deflector device.
A reference plane may be formed, for example, by a second optical fiber, a light source or a light receiver. Adjustable positioning of, for example, the end faces of optical fibers with respect to one another is important for numerous measuring-technical applications.
For example, the amount of light carried by optical fibers can be varied in a controlled manner by offsetting the end faces of two facing optical fibers in the axial direction (the so-called variable coupling method). The precision of the adjusting member and the offset are critical variables in the sub-micron range. Furthermore, variable coupling requires fibers with smooth and higher parallel end faces. These requirements become more severe as the refractive index difference between the fibers and the medium between the fiber end faces increases.
In all applications the efficiency of use of optical fibers depends on whether the end faces of the optical fibers can be accurately positioned in a reproducible manner. For example, mechanical devices such as x-y-z translators, concentric tubes of V-groove devices are known to be used for this purpose. Such mechanical positioning devices have drawbacks such as, for example, play between the components of the device, hysteresis effects, comparatively high manufacturing costs and in many cases also insufficient reliability.
German Offenlegungsschrift No. 3103010 (corresponding to U.S. Pat. No. 4,543,663) discloses a device for positioning the end of an optical fiber within a range of positions. This device comprises a deflector device which includes at least one piezoelectric deflector element. A first end of the deflector element is arranged for connection to one or more ends of one or more optical fibers. A second end of the deflector element is situated at reference position. When a suitable amount of electric energy is applied to the piezoelectric deflector element, it assumes a given position from the range of positions. The device does not allow for relative displacement of the end faces of two optical fibers without causing a change of the tilting angle between the end faces, so that angular errors occur in this known device.